Acceleration responsive switching circuit



Nov. 11, 1958 R. R. CAMPBELL .ACCELERATION RESPONSIVE SWITCHING cmcun Filed Sept. 28, 1956 comm M .5 mw

ROBERT R. CAMPBELL INVENTOR ATT RNEYS United States Patent AGGELERATIONRESPONSIVE 'SW IT CHTNG CIRCUIT RobertRicardo. Campbell,.Baltimore, MdQ, assignor to Bendix Aviation Corporation, Towson, Md., a corporation of Delaware This invention relates to switching circuits and more particularly to such circuits employing transistors and operable with a timedelay which varies in response to the magnitude and-rate of the movement of a mechanical element.

v Itlis an object of the 'invetion to provide a transistor switching circuit of the above type which responds to accelerations of a mechanical element above a selected rate and which is simple and reliable.-

V This and other objects and advantages of the invention are realizedby a transistor circuit including a relay; in the collector circuit thereof and a capacitor in the base circuit which charges through the base to emitter resistance of the transistor in response'to the variation of a resistor by movement of said mechanical element.

In the d'rawingz Fig. 1 isv a schematic diagram of a circuit embodying the invention and illustrating one use thereof and Fig. 2 is a perspective view of a-portion of the intake manifold of an internal combustion engine, having associated. therewith control elements of the circuit of Fig. 1.

. In the drawing there is shown a shaft 1 which is driven insynchronism with the operation of an internal combustion engine and-maybe the distributor shaft. thereof. Carried by the shaft 1 for rotation therewith is a lobed cam 2 having one lobe for each cylinder of the engine 2,859,738 Patented, Nov l 1, 1.9.58

16; and,..applied by. wayof a conductor 25 to an amplifier 26. and thence by way of a conductor 27. to a wiping contactelementilfl carried by and insulated from anarm 3'1 whichi s mounted-on the shaft 1. for rotation. there? with... :The .contact element 30. sequentially. wipes a pluralityfof. contact.segments..32 of which thereis one for each cylinder of the engine. Only twoof these are shown in the drawing. Each, segment 32 is. connected toone terminal of; a, solenoidcoil, 33. having. an armature 34. The...remainingjterminalof each solenoid. coil is corinected to. the yoltage. reference plane. The, lower end of each armature. terminates in avalveelement 35 which seats in a-.valve seat36 formed inthe intake maniw foldof the. internal combustion engine adjacent tothe intake. valve. of, a. respective cylinder thereof.

' Theslider of. the variable resistor: 24 is: mechanically connectedby a linkage 37 to a piston 40which is driven in. response.- to, the. manifold vacuum. of the engine. Connected, across, the terminals of the resistor 23 is a relayooperatedswitch. 41. which is normally in a closed position. The switchisoperated by a relay; coil- 42, one terminal, of which: isconnected to the voltage reference plane. and theother terminal to the collector electrode of: a; transistor 43. The emitter electrode of thisrtransistor. is.connec tedto. the conductor 7 by the conductor 44....Thebase.electrode is. connected to the conductor and driving, by means of a mechanical linkage 3, one. 7

contact element of a single pole, single throw switch 4. This contact is connected to a voltage reference plane indicated as the ground 5. The other contact is connected to a voltage reference plane indicated as the ground 5. The other contact is connected by way of a resistor 6 and a conductor 7 to the positive terminal 8 of a source of supply voltage which is shown as having a value of twelve volts conforming to the usual automobile battery.

The said other contact of the switch 4 is also connected to one terminal of a capacitor 10, the remaining terminal of which is connected to the conductor 7 by Way of a resistor 11 and to the cathode of a diode 12. The anode of the diode 12 is connected to the base electrode of a transistor 13 and is further connected to the conductor 7 by way of a resistor 14 and to the voltage reference plane by way of a resistor 15.

The emitter electrode of the transistor 13 is connected to the emitter electrode of a second transistor 16 and their junction is connected by a resistor 17 to the conductor 7. The collector electrodes of transistors 13 and 16 are connected to the voltage reference planeby way of respective resistors 20 and 21. The collector of transistor 13 is also connected to the base electrode of transistor 16 by way of capacitor 22. The base electrode of transistor 16 is connected to the ground reference plane by Way of resistor 23 and a variable resistor 24 in series.

The transistors 13 and 16 and their associated components form a monostable multivibrator, the output of which is taken from the collector electrode of transistor 7V througha-resistor 45. This electrode is also connected by way, of a resistor 46. and. a capacitor 47 in series to the movable'contact 48 of a variable resistor 49 having one. of its terminalsconnected to the, conductor 7 and the other to the voltage reference plane. The movable contaet48isdriventhrougha mechanical linkage 50, 52 from. the accelerationpedal 51 of the engine, which also controls the position. of throttle valve 53 in the intake manifold 54, by way -of linkage element 52 and crank arm 55. in. the, operation of the. device described above the switch 4\.is openedand. closedonce while the contact element 3.0 is wiping each of the, segments 32. When; the switch is closed the upper contact, as'illustrated, is placed .at .the voltage of the ground reference plane. When the. switch. isv open it assumes the voltage of the terminal 8. This results in a voltage of square waveform. as indicated at 52. The waveform 52 is differentiatedabythe elements 10 and 11 and the negative-going. spikesof this differentiated waveform are applied through the low impedance of the diode 12 to the base electrode of the transistor 13.

Prior to the application of this triggering spike of voltage, the transistor 16 is conducting to saturation; The conduction of transistor 16. creates a voltagedrop across, the resistor 17 which results in a base to emitter current flow in transistor 13. sufficient to maintain that transistor cutoff. In, this situation the capacitor 22 will be charged, asindicated, charging through resistors 20 and 17 and the base to emitter resistance of transistor 16. When a negative trigger is applied to the base electrode of the transistor 13 a regenerative action occurs in which conduction is initiated in the transistor 13 resulting in a partial discharge of the capacitor 22 and a lessening of the conduction of transistor 16. This regenerative action culminates in the conduction of the transistor 13 to saturation and the cut off of transistor 16. The length of time during which transistor 16 will remain in the state of cut off is determined by the values of resistors 23 and 24, when both are in the circuit, but normally by resistor 24 alone.

The output of the multivibrator being applied through the amplifier 26, conductor 27, element 30 and segment 32 to one of the solenoid coils 33, lifts its armature 34, thus opening the valve 35 and allowing fuel under preS-. sure to be injected through the valve.

The portion of the circuit, the operation of which has just been described, is disclosed in application Serial No. 608,798, filed September 10, 1956, in the name of Noble F. ,Pribble and entitled, Driver Circuit. for Fuel In: jector. It'is disclosed here to illustrate one use to which the invention may be put. The portion of the "circuit, the operation of which will now be described, isthe portion embodying the present invention.

The purpose of the instant invention is toswitchan element into or out of a circuit by electronic means. The element so switched is illustrated here as the resistor 23 in the base circuit of transistor 16. As shown in the drawing, with. the switch 41 in its closed. state, the resistor 23 is out of the circuit. Under certain conditions of operation of a fuel injection control circuit, such as a sudden, acceleration demand, it is desirable to provide a drastic increasein the duration of the multi vibrator output pulse beyond that which would result from normal throttle action. 'This can be accomplished by inserting the resistor 23 into the circuit. This insertion is accomplished here in response to operation of the accelerator pedal 51 at a rate in excess in a selected value. The potentiometer .49 is connected to the pedal 51 by a linkage 50. The transistor 43 is normally cut off. -When the pedal 51 is rapidly depressed, moving the slider 48 toward the voltage reference plane, the capacitor 47 charges with the polarity shown, through resistor 46 and the low base to emitter resistance of the transistor 43. The charging current from emitter to base causes collector current to flow which actuates the relay coil 42 and opens switch 41. This abruptly lengthens the duration of the output pulse of the multivibrator. The relay remains activated until the charging current flowing from the emitter to the base drops and causes the collector current also to drop.

A circuit with values as shown will allow the'relay to be activated for two seconds when the slider 48 on resis-' tor 49 is quickly moved over the length of the resistor. A very slow movement of the slider will not result in activation of the relay.

The values applied to the various components are for the purpose of indicating typical suitable values and should not be considered as restricting the invention.

What is claimed is:

-1. Means for activating a relay in response to movement of a mechanical element in excess of a selected rate and maintaining its activation for a time which is a function of the magnitude and rate of said movement, comprising: a transistor, a relay coil in the output circuit thereof, an energy storage means in the input circuit thereof, means applying a D. C. potential to said storage element and means varying the magnitude of. said potential in accordance with movement of, said element.

2. Means for activating a relay in response to movement of a mechanical element in excess of a selected rate and maintaining its activation for a time which is a function of the magnitude and rate of said movement, comprising: a transistor, a relay coil in the collector circuit thereof, a capacitor in the base circuit thereof,

means applying a D. C. potential to said capacitor and means varying the magnitude of said potential as a function of the movement of said element.

3. Means for activating a relay in response to movement of a mechanical element in excess of a selected rate and maintaining its activation for a time which is a function of the magnitude and rate of said movement, comprising: a transistor, a relay coil in the collector circuit thereof, a capacitor in the base circuit thereof, means including a potentiometer applying a D. C. potential to said capacitor and a mechanical linkage between the slider of said potentiometer and said element.

4. A monostable multivibrator, means triggering said multivibrator into its unstable state and means for controlling the duration of said unstable state, comprising: an impedance element in an input circuit of said multivibrator, means short circuiting said element, a switch in the last named means, and operating means forsaid switch comprising a relay coil positioned to open said switch when activated, a transistor, means connecting said coil in an output circuit of said transistor, an energy storage element in an input circuit of said transistor, a

movable element, means applying a D. C. potential to said storage element and means varying the magnitude of said potential in accordance with movement of said movable element.

5. In a system for injecting measured amounts of fuel into the cylinders of an internal combustion engine having an air throttle, said system including a solenoid operated valve for each cylinder of said engine, means applying fuel under constant pressure to said valves, and means opening said valves in synchronism with the operation of said engine; means controlling the duration of the open time of said valves, the last named means comprising: a monostable multivibrator, means triggering said multivibrator into its unstable state in synchronism with the operation of said engine, means applying the'output pulses of said multivibrator sequentially to the respective solenoids of said valves and means con trolling vthe. .duration of said output pulses, the last named means. comprising a first impedance'element in an input circuit of said multivibrator, means varying the impedance of said element as a function of the manifold vacuum of said engine, a second impedance element in an input circuit of said multivibrator, means normally short-circuiting said second impedance element, the last named means comprising a switch, a relay coil positioned to open said switch when activated, an amplifier circuit having input and output circuits, means connecting said relay coil in said output circuit of said ampliler, an energy storage element in said input circuit of said amplifier, means applying energy to said storage means, operating means for the air throttle of said engine and means varying the operation of said energy applying means in accordance with the movement of said air throttle operating means.

No references cited. 

